scholarly journals Study on the Decomposition Mechanism of Natural Gas Hydrate Particles and Its Microscopic Agglomeration Characteristics

2018 ◽  
Vol 8 (12) ◽  
pp. 2464 ◽  
Author(s):  
Xiaofang Lv ◽  
Bohui Shi ◽  
Shidong Zhou ◽  
Shuli Wang ◽  
Weiqiu Huang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Gas Hydrate ◽  
Length Distribution ◽  
Chord Length ◽  
Low Flow ◽  
Natural Gas Hydrate ◽  
Reflectance Measurement ◽  
Chord Length Distribution ◽  
Water Cut

Research on hydrate dissociation mechanisms is critical to solving the issue of hydrate blockage and developing hydrate slurry transportation technology. Thus, in this paper, natural gas hydrate slurry decomposition experiments were investigated on a high-pressure hydrate experimental loop, which was equipped with two on-line particle analyzers: focused beam reflectance measurement (FBRM) and particle video microscope (PVM). First, it was observed from the PVM that different hydrate particles did not dissociate at the same time in the system, which indicated that the probability of hydrate particle dissociation depended on the particle’s shape and size. Meanwhile, data from FBRM presented a periodic oscillating trend of the particle/droplet numbers and chord length during the hydrate slurry dissociation, which further demonstrated these micro hydrate particles/droplets were in a dynamic coupling process of breakage and agglomeration under the action of flow shear during the hydrate slurry dissociation. Then, the influences of flow rate, pressure, water-cut, and additive dosage on the particles chord length distribution during the hydrate decomposition were summarized. Moreover, two kinds of particle chord length treatment methods (the average un-weighted and squared-weighted) were utilized to analyze these data onto hydrate particles’ chord length distribution. Finally, based on the above experimental data analysis, some important conclusions were obtained. The agglomeration of particles/droplets was easier under low flow rate during hydrate slurry dissociation, while high flow rate could restrain agglomeration effectively. The particle/droplet agglomerating trend and plug probability went up with the water-cut in the process of hydrate slurry decomposition. In addition, anti-agglomerates (AA) greatly prohibited those micro-particles/droplets from agglomeration during decomposition, resulting in relatively stable mean and square weighting chord length curves.

scholarly journals Effect of Pre-Shear on Agglomeration and Rheological Parameters of Cement Paste

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2173
Author(s):  
Mareike Thiedeitz ◽  
Inka Dressler ◽  
Thomas Kränkel ◽  
Christoph Gehlen ◽  
Dirk Lowke
Keyword(s):  
Yield Stress ◽  
Mixing Time ◽  
Length Distribution ◽  
Chord Length ◽  
Rheological Parameters ◽  
Reflectance Measurement ◽  
Time Dynamic ◽  
Chord Length Distribution ◽  
In Situ Investigation

Cementitious pastes are multiphase suspensions that are rheologically characterized by viscosity and yield stress. They tend to flocculate during rest due to attractive interparticle forces, and desagglomerate when shear is induced. The shear history, e.g., mixing energy and time, determines the apparent state of flocculation and accordingly the particle size distribution of the cement in the suspension, which itself affects suspension’s plastic viscosity and yield stress. Thus, it is crucial to understand the effect of the mixing procedure of cementitious suspensions before starting rheological measurements. However, the measurement of the in-situ particle agglomeration status is difficult, due to rapidly changing particle network structuration. The focused beam reflectance measurement (FBRM) technique offers an opportunity for the in-situ investigation of the chord length distribution. This enables to detect the state of flocculation of the particles during shear. Cementitious pastes differing in their solid fraction and superplasticizer content were analyzed after various pre-shear histories, i.e., mixing times. Yield stress and viscosity were measured in a parallel-plate-rheometer and related to in-situ measurements of the chord length distribution with the FBRM-probe to characterize the agglomeration status. With increasing mixing time agglomerates were increasingly broken up in dependence of pre-shear: After 300 s of pre-shear the agglomerate sizes decreased by 10 µm to 15 µm compared to a 30 s pre-shear. At the same time dynamic yield stress and viscosity decreased up to 30% until a state of equilibrium was almost reached. The investigations show a correlation between mean chord length and the corresponding rheological parameters affected by the duration of pre-shear.

scholarly journals Effects of Reservoir Parameters on Separation Behaviors of the Spiral Separator for Purifying Natural Gas Hydrate

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5346
Author(s):  
Shunzuo Qiu ◽  
Guorong Wang
Keyword(s):  
Particle Size ◽  
Natural Gas ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Gas Hydrate ◽  
Volume Fraction ◽  
Differential Pressure ◽  
Separation Performance ◽  
Recovery Efficiency ◽  
Natural Gas Hydrate

The spiral separator is an important tool for desanding in natural gas hydrate production, and the change of hydrate reservoir parameters has a great impact on spiral separator behavior. Mastering the influence law is helpful to improve the separation performance. Until now, there was still no detailed analysis of the effect mechanism between reservoir parameters and spiral separator behavior. In this paper, a downhole spiral separator was designed. Then, the effects of reservoir parameters (particle size, hydrate, volume fraction, and sand volume fraction) on separation performance (discrete phase distribution, separation efficiency, and differential pressure) with different flow rates were investigated by numerical simulation method Fluent 18.0. The results show that effects degree of reservoir parameters is in order from large to small: sand phase volume fraction, particle size, hydrate volume fraction. As the particle size increases, the separation performance is improved. When the sand volume fraction increases, the natural gas hydrate (NGH) recovery efficiency and differential pressure both increase, but the sand removal efficiency decreases. When the hydrate fraction increases, the separation performance change law is opposite to that when the sand volume fraction increases. In addition, with increasing the flow rate, the efficiency and differential pressure increase. Therefore, reservoir saturation and porosity can balance NGH recovery efficiency and sand removal efficiency. Furthermore, the spiral separator has good performance under the change of reservoir parameters. The performance of the NGH spiral separator can be also maintained by increasing the flow rate.

scholarly journals Study on axial-flow hydrocyclone for in-situ sand removal of natural gas hydrate in the subsea

2021 ◽  
Vol 245 ◽  
pp. 01050
Author(s):  
Haitao Lin ◽  
Yuan Huang ◽  
Hualin Wang
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Gas Hydrate ◽  
Separation Zone ◽  
Separation Performance ◽  
Natural Gas Hydrate ◽  
Inlet Flow ◽  
Zone Length ◽  
Inlet Flow Rate

Natural gas hydrate (NGH) has become the most potential emerging green energy known in the 21st century due to its characteristics of wide distribution, abundant reserves and clean combustion. This study designs an axial annulus in situ hydrocyclone desander (AAIHD) based on drilling instruments in order to resolve the serious problem of sand production during solid fluidization of NGH. The effect of the inlet flow rate and separation zone length on the sand removal efficiency of the AAIHD is tested through experimental research. The results indicate that AAIHD has a higher separation performance when the separation zone length is L/D=12.4 and the inlet flow rate is in the range of 10 m3/h to 25 m3/h, and the maximum separation efficiency reaches 77.4%. The purpose of this study is to achieve in-situ sand removal and the backfilling of sand slurry in addition to facilitate the advancement of solid fluidized exploration technologies.

Experimental Study on Natural-Gas-Hydrate-Slurry Flow

SPE Journal ◽  
2013 ◽  
Vol 19 (02) ◽  
pp. 206-214 ◽  
Author(s):  
X.F.. F. Lv ◽  
J.. Gong ◽  
W.Q.. Q. Li ◽  
B.H.. H. Shi ◽  
D.. Yu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Length Distribution ◽  
Hydrate Formation ◽  
Diesel Oil ◽  
Slurry Flow ◽  
Flow Loop ◽  
Reflectance Measurement ◽  
System Pressure ◽  
Series Of Experiments ◽  
Water Cut

Summary To better understand hydrate-slurry flow, a series of experiments was performed, including water, natural gas, and diesel oil, under 4-MPa system pressure and 1.25-m/s initial linear velocity. The experiments have been conducted in a high-pressure hydrate-flow loop newly constructed at China University of Petroleum (Beijing), and dedicated to flow-assurance studies. A focused-beam reflectance measurement (FBRM) probe is installed in this flow loop, which provides a qualitative chord length distribution (CLD) of the particles/droplets in the system. First, the influence of flow rate on the hydrate-slurry flow was discussed. Then, we studied other influencing factors—such as water cut and additive dosage—on the hydrate induction period and the CLD before/after hydrate formation. Third, a new correlation was fitted between the dimensionless rheological index n′ and water cut as well as additive dosage, according to these experimental data. Finally, a laminar-flow model for the prediction of the pressure drop for the quasisingle-phase hydrate slurry was established, and tested by comparison with the experimental results in this paper.

scholarly journals Evaluation and re-understanding of the global natural gas hydrate resources

2021 ◽  
Vol 18 (2) ◽  
pp. 323-338
Author(s):  
Xiong-Qi Pang ◽  
Zhuo-Heng Chen ◽  
Cheng-Zao Jia ◽  
En-Ze Wang ◽  
He-Sheng Shi ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Hydrate ◽  
Oil And Gas ◽  
Material Balance ◽  
Energy Resource ◽  
Resource Assessment ◽  
Future Trend ◽  
Natural Gas Hydrate ◽  
The Future ◽  
Recoverable Resources

AbstractNatural gas hydrate (NGH) has been widely considered as an alternative to conventional oil and gas resources in the future energy resource supply since Trofimuk’s first resource assessment in 1973. At least 29 global estimates have been published from various studies so far, among which 24 estimates are greater than the total conventional gas resources. If drawn in chronological order, the 29 historical resource estimates show a clear downward trend, reflecting the changes in our perception with respect to its resource potential with increasing our knowledge on the NGH with time. A time series of the 29 estimates was used to establish a statistical model for predict the future trend. The model produces an expected resource value of 41.46 × 1012 m3 at the year of 2050. The statistical trend projected future gas hydrate resource is only about 10% of total natural gas resource in conventional reservoir, consistent with estimates of global technically recoverable resources (TRR) in gas hydrate from Monte Carlo technique based on volumetric and material balance approaches. Considering the technical challenges and high cost in commercial production and the lack of competitive advantages compared with rapid growing unconventional and renewable resources, only those on the very top of the gas hydrate resource pyramid will be added to future energy supply. It is unlikely that the NGH will be the major energy source in the future.

scholarly journals pH Effect of Natural Gas Hydrate on X80 Steel Solid—Liquid Phase Scouring Corrosion

ACS Omega ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 3017-3023
Author(s):  
Song Deng ◽  
Dingkun Ling ◽  
Binbin Zhou ◽  
Yu Gong ◽  
Xin Shen ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Natural Gas ◽  
Gas Hydrate ◽  
Ph Effect ◽  
Natural Gas Hydrate ◽  
X80 Steel ◽  
Solid Liquid
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